Language evolution seminar

Speaker: Marieke Woensdregt (University of Edinburgh)

Title: A model of cultural co-evolution of language and perspective-taking

Abstract: Language relies on mindreading (a.k.a. theory of mind), as language users have to entertain and recognise communicative intentions. Mindreading abilities in turn profit from language, as language provides a means for expressing mental states explicitly, and for transmitting one’s understanding of minds to others (e.g. younger members of the population). Given this interdependence, it has been hypothesised that language and mindreading have co-evolved. I will present an agent-based model to formalise this hypothesis, which combines referential signalling with perspective-taking. In this model, agents’ communicative behaviour is probabilistically determined by an interplay between their language and their perspective on the world. In order to learn the language, learners thus have to simultaneously infer both the language and the perspective of the speaker they're receiving input from (using Bayesian inference). Simulation results show that learners can solve this task by bootstrapping one from the other, but only if the speaker uses a language that is at least somewhat informative.

The question then becomes under what circumstances a population of these agents can evolve such an informative language from scratch. We explore two different selection pressures: a pressure for successful communication and a pressure for accurate perspective-inference. We also compare two different types of agents: literal communicators and pragmatic communicators. Pragmatic speakers optimise their communication behaviour by maximising the probability that their interlocutor will interpret their signals correctly, given their model of the interlocutor's language and perspective. Iterated learning results show that literal agents can evolve meaningful linguistic conventions both under a pressure for communication and under a pressure on perspective-inference. The same results were found for pragmatic agents, except that pragmatic agents can achieve equally high levels of success at communicating and inferring perspectives with much more ambiguous languages, because these agents can compensate for suboptimal languages using their pragmatic ability. Time permitting, I will also present some preliminary results on the evolvability of this pragmatic ability.

Contact

Seminars are organised by the Centre for Language Evolution

Andres Karjus

Centre for Language Evolution